Protein phosphorylation is one of the extremely important posttranslational modifications on a variety of cellular functions including cell proliferation.Therefore, the identification ofphosphoproteins and the phophorylated sites is important research issue.However, it is difficult to detect phosphoprotein by mass spectrometry analysis as it hardly exists in cells and is difficult to be ionized.Therefore, the selective enrichment of phosphopeptide becomes necessary.Currently, methods such as IMAC and metal oxide chromatography are widely used to enrich phosphopeptides as these methods have high affinity to phosphopeptides.However, the enrichment efficiency in these methods depends on pH, the content of organic solvents, additives to the sample solvents, the sample loading speed and so on.